Please check my answers :) (Factoring)

Factor completely:

1. 5k^{3}- 40

5(k-2)(k^{2} + 2k + 4)

2. t^{2} - 81/169

(t + 9/13)(t - 9/13)

3. 12b^{2}+ 36b + 27

(2b+3)2

4. b^{4}- 16

(b^{2} +4)(b+2)(b-2)

82. (2k-7)h^{2 }- 4 (2k-7)h-45(2k-7)

(2k-7)(h+5)(h-9)

Thank you :)

Re: Please check my answers :) (Factoring)

Correct except that you have lost a factor of 3 in no.3 Should be 3(2b+3)^2

Re: Please check my answers :) (Factoring)

Quote:

Originally Posted by

**Kibbygirl** Factor completely:

1. 5k^{3}- 40

5(k-2)(k^{2} + 2k + 4)

Yes, that is correct.

Quote:

2. t^{2} - 81/169

(t + 9/13)(t - 9/13)

Yes, that is correct.

Quote:

3. 12b^{2}+ 36b + 27

(2b+3)2

No, that is not correct. What you have written is the same as 2(2b+ 3)= 4b+ 6 (multiplication is commutative). What I think you meant was

(2b+ 3)^{2} but that is still incorrect. (2b+ 3)^{2}= (2b)^{2}+ 2(2b)(3)+ 3^{2}= 4b^{2}+ 12b+ 9. Did you leave out a "3" that you factored out first? 12b^{2}+36b+ 27= 3(4b^{2}+ 12b^{2}+ 9)= 3(2b+ 3)^{2}.

Quote:

4. b^{4}- 16

(b^{2} +4)(b+2)(b-2)

Yes, this is correct.

Quote:

82. (2k-7)h^{2 }- 4 (2k-7)h-45(2k-7)

(2k-7)(h+5)(h-9)

Yes, that is correct.